The present disclosure generally relates to the field of electronically controlled valves. The present disclosure relates more specifically to a power failure controller for an electronically controlled expansion valve in a refrigeration system.
In some refrigeration systems, the expansion valve is electronically controlled. For example, an electronically controlled stepper motor may be configured to variably actuate the valve between an opened position and a closed position. The controller (i.e., control module, control circuit, etc.) that controls the motor can be configured to open or close the valve based on commands from an upstream control system, one or more feedback or feed forward loops utilizing temperature sensors, pressure sensors, or other inputs to the loop, or any other control logic activities. For example, the “Smart Valve” product sold by Hill Phoenix, Inc. automatically adjusts superheat to pre-determined target values based on the application (e.g., low or medium-temperature operation); it can automatically regulate the superheat in response to changing ambient conditions, system parameter changes, and refrigeration case load changes.
Applicants have identified a need to close the electronically controlled expansion valve in a controlled manner in the event of a power failure.